# <A timestep of size zero was assigned on the integer timeline!> Checked smoothing lengths are non-zero

From: DIXON J.B. <jonathan.dixon_at_durham.ac.uk>
Date: Mon, 7 Jan 2013 09:56:59 -0000

All,

I am having a problem I hope you can help me with..

I'm running a basic simulation of a disc galaxy forming with 100,000 particles and getting the following error:

Begin Step 0, Time: 0, Systemstep: 0
domain decomposition...
NTopleaves= 344
domain decomposition done.
begin Peano-Hilbert order...
Peano-Hilbert done.
Start force computation...
Tree construction.
Tree construction done.
Begin tree force.
tree is done.
Begin tree force.
tree is done.
Start density computation...
ThisTask=0: Need to do a second neighbour loop for (0.0514353|-0.225033|-0.00548556) hsml=0.7 no=36679
ThisTask=0: Need to do a second neighbour loop for (0.0486755|-0.226033|-0.00132951) hsml=0.7 no=36725
ThisTask=0: Need to do a second neighbour loop for (0.0443219|-0.230982|-0.00975273) hsml=0.7 no=36717
ThisTask=0: Need to do a second neighbour loop for (0.0387366|-0.238146|-0.00368765) hsml=0.7 no=36659
ThisTask=0: Need to do a second neighbour loop for (0.0436788|-0.238358|-0.00278879) hsml=0.7 no=97435
.
.
. (Lots more output here)
.
ThisTask=0: Need to do a second neighbour loop in hydro-force for (0.0421819|-0.239535|0.00401269) hsml=0.7 no=90617
ThisTask=0: Need to do a second neighbour loop in hydro-force for (0.0457042|-0.226046|0.000454599) hsml=0.7 no=25608
ThisTask=0: Need to do a second neighbour loop in hydro-force for (0.0457325|-0.229131|0.00956516) hsml=0.7 no=25610
force computation done.

Error: A timestep of size zero was assigned on the integer timeline!
We better stop.
Task=1 Part-ID=54529 dt=9.09641e-09 tibase=1.86265e-08 ti_step=0 ac=6.04269e+14 xyz=(0.101498|-2.55188|-0.00968288) tree=(-2.53342e+13|6.0373e+142.9378e+12)

hydro-frc=(-197733|59003.1|-17028.6)
task 1: endrun called with an error level of 818

Error: A timestep of size zero was assigned on the integer timeline!
We better stop.
Task=0 Part-ID=1050 dt=1.62322e-08 tibase=1.86265e-08 ti_step=0 ac=1.89764e+14 xyz=(-0.269647|-4.84833|-0.00568618) tree=(1.03536e+13|1.89481e+142.57818e+11)

hydro-frc=(-13511.4|4029.45|-121.305)
task 0: endrun called with an error level of 818

--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 818.

I have had a look at some previous entries to this list and they suggest checking that the smoothing lengths are all non-zero: this I have done and all the relevant smoothing lengths are indeed non-zero.

Any help much appreciated! All the best,

Jono